Light sensitive device



Aug. 8, 1944. H. ABRAMsoN ErAL LIGHT SENSITIVE DEVICE Filed Feb. 5, 1941Patented Aug. 8, 1944 LIGHT SENSITIVE DEVICE Hugo Abramson, Esklstuna,and Carl Eckers, Stockholm, Sweden, assignors to American GasAccumulator Company, Elizabeth, N. J., a corporation of New JerseyApplication February 3, 1941, Serial No. 377,202 In Sweden October 3,1939 (Cl. 20D-140) 4 Claims.

Our invention relates to improvements in light sensitive devicesfor'controlling the operation of any desired apparatus, such aslightbuoy, beacon, street illumination system or the like.

Heretofore it has been proposed to provide a device of this type whichincludes a pair of connected containers which are partially filled withliquid with vapor trapped above the liquid in each vessel. One of thesevessels is arranged to absorb heat at a faster rate than the other,whereby the vapor trapped therein expands and forces some of the liquidinto the other vessel. The vessels are pivotally mounted in such a waythat the unbalance resulting from displacement of the liquid from onevessel to the other causes the vessels to pivot and thus operate acontrolling member, such as a mercury switch. However, devices of thisnature have had the drawback that a substantial amount of work wasrequired to force the liquid from one chamber to the other and suchdisplacement of the liquid shifted the center of gravity of the pivotedcontainers with the result that a substantial amount of the forceproduced by the unbalance was not available for actuating thecontrolling member.

In accordance with our present invention the containers are constructedin the form of a portion of a torus. The upper part of the torus isinterrupted and sealed. The torus is pivotally mounted in a verticalplane about an axis which coincides with the geometrical center of thetorus. Also,'the interior diameter of the torus is uniform throughout,thereby reducing to a minimum the resistance to the flow of liquidtherethrough. In addition, the torus and associated parts which pivotwith it are balanced about the axis of rotation in such a Way that thecenter of gravity always coincides with the axis. Consequently, the onlyforce required to pivot the container is that necessary to overcomefriction in the bearing` and the slight friction between the flowingliquid and the interior and the torus.

Further objects and advantages of my invention will be apparent from thefollowing description considered in connection with the accompanyingdrawing, which form a part of this specification and of which:

Fig. 1 is a side View, partially in cross-section, of a device inaccordance with our invention; and

Fig. 2 is a top view, partially in cross-section, of the device shown inFig. 1.

Referring to the drawing, reference character I0 designates a base platewhich is provided with threaded bores II for securing the plate in placeon any suitable standard. The base plate car- LI O ries a pair ofupright members I2 which are provided at their upper ends withknife-edge supports I3. A shaft I4 s supported by the knife edges, whichengage V-shaped recesses I5 formed in the shaft. A strap I6 is securedto each of the members I2 and surrounds the shaft I4 in order to preventaccidental displacement of the shaft from the knife edges. A pair ofarms I 'I is rigidly secured to the shaft I4 and is provided withadjustable stops I8 which may contact one of the uprights I2 so as tolimit the pivotal movement of the shaft.

A member I9 is secured at its center to the shaft and at its ends to atubular member 20 which is in the form of approximately threequarters ofa torus. As is clear from Fig. 1, this torus is interrupted at the upperpart thereof, and the ends of the tube are sealed by means of plugs 2Iand 22. The geometrical center of the torus coincides with the center ofrotation of the shaft I4.

The tube 20 is preferably made of stainless steel having a small wallthickness of, for instance, 0.5 mm. The right hand half of the torus, asviewed in Fig. 1, is painted black or otherwise given a high coefficientof heat absorption, while the other half is given a lower coefficient,as by being chromium plated or highly polished. The tubular member 20 isabout half filled with a suitable liquid. The vapor of this liquidshould have a high coefficient of expansion, the liquid should notattack the stainless steel tube, it should have a low freezing point(not above -50 C.) if the device is to be used outdoors, and itscritical temperature should not be below 70 C. We have found thatsulphur dioxide has all of these characteristics. However, beforeplacing the sulphur dioxide in the tubular member 20, the latter shouldbe heated so as to expel all moisture and as much air as possible inorder to prevent the formation of sulphuric acid.

Secured at right angles to the member I9 is an arm 23, the lower end ofwhich carries a mercury switch 24. The glass tube of this switch ispreferably arcuate with its center coinciding with the center ofrotation of shaft I4. Flexible leads 25 and 26 connect the terminals ofthe switch with the terminal blocks 2l and 28, respectively, which aresecured to the base plate I0.

The upper end of the arm 23 carries an adjustable counter-weight 29which is so dimensioned and positioned on the arm as to exactly balanceall of the elements carried by the shaft I4. In order words, the centerof gravity of the pivoted structure coincides with its center ofrotation.

A screw 30 extends through a threaded bore in the base plate locatedjust below the bottom of the torus. This screw may be advanced upwardlyso as to contact the torus and lift the shaft I4 from the knife edgesand clamp it against the straps I6 to prevent pivoting of the structureduring shipment. The base plate is preferably provided with aventilation hole 3| covered by a wire mesh screen, and a transparentdome 32 is secured thereto by means of a ring 33 fastened to the baseplate by bolts 34. The dome protects the device from dust and the actionof the weather while exposing the torus to light and radiant heat.

If the device is to be responsive to sun-light, it is preferablypositioned with the plane of the torus extending in a north and southdirection and with the heat absorbing portion of the torus to the south.In this position the heat absorbing portion will always be exposed tothe sunlight and will never be in a shadow cast by the nprights l2 orthe other portion of the torus. The above positioning is correct, if thedevice is located in the Northern Hemisphere, `but obviously if it isused in the Southern Hemisphere it should be turned around, inasmuch asthe sun shines from the north.

At night, when the torus is not exposed to radiant heat, both portionsthereof will have approximately the same temperature and the vapor abovethe liquid in each end of the torus will occupy the same volume.Consequently, the torus and other pivotal structure occupies theposition shown in Fig. 1 and the liquid mercury within the switch 24bridges the contacts and closes the circuit so as to light the buoy orother apparatus which the device is employed to control. However, duringdaylight when the torus is exposed to the radiant heat of the sun, theright hand portion of the torus, which is blackened, absorbs more heatthan does the left hand polished portion. This causes the vapor abovethe liquid in the right hand portion to expand more than the Vapor inthe other portion, which in turn causes liquid to be displaced from theright to the left hand portion. This results in a pivoting of the torusin a counter-clockwise direction, whereby the mercury in the switch runsto the left hand end of the tube and opens the circuit through theswitch.

Due to the fact that the geometrical center of the torus coincides withits center of rotation, and the center of the torus coincides with itscenter of rotation, the center of gravity of the device is not shiftedby the above described displacement of the liquid, but always coincideswith the center of rotation. Moreover, due to the fact that the internaldiameter of the torus is uniform throughout, it oiiers a minimumresistance to flow of liquid from one portion of the torus to the other.Thus, practically all of the force resulting from the imbalance causedby the liquid displacement is available for shifting the switch. Due tothe fact that the tube of the switch is arcuate with its centercoinciding with the center of rotation, the shifting of the liquidmercury therein does not disturb the center of gravity of the entiredevice.

While we have shown the device as used to operate an electric switch, itis obvious that it could also be used to open and close a valve forcontrolling flow of gas or other fluid fuel. It is to be understood thatthe embodiment described is for the purpose of illustration only andthat the scope of our invention is not to be limited thereby, but is tobe determined by the appended claims.

What we claim is:

1. In a device of the class described, a container in the shape of atorus interrupted at its upper part, means for pivotally mounting saidtorus about an axis coinciding with its geometric center, said torusbeing partially lled with a liquid and opposite portions of said torushaving different light absorbing characteristics, and a control memberactuated by pivoting of said torus.

2. In a device of the class described, a container in the shape of atorus interrupted at its upper part, means for pivotally mounting saidtorus about an axis coinciding with its geometric center, the portionsof said torus on opposite sides of said center having diiierent lightabsorbing characteristics, said torus being partially filled with aliquid and having a uniform cross-sectional area whereby liquid may nowfrom one portion to the other with a minimum of resistance, and acontrol member actuated by pivoting of said torus.

3. In a device of the class described, a container in the shape of atorus interrupted at its upper part, means for pivotally mounting saidtorus about an axis coinciding with its center, said torus beingpartially filled with a liquid and opposite portions of said torushaving different light absorbing characteristics, a control memberconnected to said torus and actuated by tilting thereof, and means forcounterbalancing said torus and associated parts so that the center ofgravity thereof coincides with said axis.

4. In a device of the class described, a container forming approximatelythree-quarters of a torus and being interrupted at its upper part, meansfor pivotally mounting said torus in a vertical plane about an axiscoinciding with its geometrical center, the portions of said torus onopposite sides of said center having different light absorbingcharacteristics, said torus being partially iilled with a liquid andhaving a uniform crosssectional area whereby liquid may flow from oneportion to the other with a minimum of resistance, acontrol memberoperable by tilting connected to said torus so as to be tilted by thepivoting thereof, and a counter-weight secured to said torus for causingthe center of gravity of said torus and associated parts which aretiltable therewith to coincide with said axis.

HUGO ABRAMSON.

CARL ECKERS.

